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Comment by fatbird | Hacker News Reader

Sorry if I keep responding, but there's a lot of interesting points in your question.

> Like how the JVM assumes classes are final and removes virtual calls until it first sees a subclass.

AFAIK, the python VM doesn't do any JITting at all. A runtime decision in the VM about handling locks is impossible at this point, I think.

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Well the user space locks he discusses already read a variable and branch between uncontended and contended cases. Specialising speculatively for single threaded would just be a third cannot-be-contended case. But yes it'd work better with a JIT - yet another reason to write one.

There is a version of Python that JITs -- I forget it's name at the moment, though.

PyPy

there are several. we (microsoft) are also trying to get an api into cpython so that anyone can use to build JITs for python. our sample implementation is at:

https://github.com/Microsoft/Pyjion

pycon 2016 talk:

https://www.youtube.com/watch?v=1DAIzO3QXcA

Sort of.

    if (threads)
         lock(...);

should still be pretty quite a bit faster than fine grained locks everywhere, since your atomics aren't broadcasting and shooting down cache lines everywhere.

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